NASA Goddard space flight center — icesat-2 mission / winter 2013
Mechanical design and engineering
Every optics experiment begins with calibrating laser-telescope for proper instrument alignment and laser collimation as vibrations and minor changes in temperature and humidity can offset these conditions. Massive 3' and 1'-diameter mirrors are moved into the lab reflect laser light the into a camera for inspection. Because the mirrors are so large and heavy, alignment is incredibly cumbersome. The whole process can take up to four hours.
My solution in place of these cumbersome mirrors was a rotary shearing interferometer, internally nicknamed the Tilt'N'Whirl. It consists of two 6" glass wedges that offset incident laser light and display the interference pattern onto a textured glass sheet. If the interference patterns, or fringes, are parallel to the shear axis of the glass wedge, then the laser light is collimated.
The Tilt'N'Whirl, a lightweight and collapsable rotary shearing interferometer for quick laser collimation inspection.
Each glass wedge is angled to inspect the interference patterns on two orthogonal shearing axes to determine proper collimation. The glass wedges sit on a linear track that rotates 360 degrees at its center. With radial travel on a rotating linear track, the glass wedges can be used to quickly inspect the quality of the 3-ft diameter incident laser light.
Custom shearing interferometer module. A machined aluminum cradle houses the glass wedge which displays interference patterns from incident light on a textured glass plate.
The two shearing interferometers sit on a linear track that rotates 360 degrees at its center.
The Tilt'N'Whirl is designed in 80/20, an easy-to-use aluminum extrusion rail system. It's lightweight and collapsable when not in use, making the laser-telescope setup much easier. The Tilt'N'Whirl reduced the setup time from up to four hours to just 30 minutes.
The Tilt'N'Whirl in its collapsed configuration used for storage.
The interferometers sit on a quick-lock/release slide. The ends of the linear track are capped in red for visibility and safety.